WO2012086009A1

WO2012086009A1 - Mode control waveguide-type laser device

Info

Publication number: WO2012086009A1
Application number: PCT/JP2010/072999
Authority: WO
Inventors: 紀之宮本; 山本　修平; 柳澤　隆行; 平野　嘉仁
Original assignee: 三菱電機株式会社
Priority date: 2010-12-21
Filing date: 2010-12-21
Publication date: 2012-06-28
Also published as: US20130121355A1; CN103098318A; EP2590276B1; JPWO2012086009A1; EP2590276A4; CN103098318B; JP5389277B2; US9197029B2; EP2590276A1

Abstract

The objective is to provide a mode control waveguide-type laser device with an increased range of control of the focal length of a generated heat lens, and with improved reliability. The laser device is equipped with: a laser medium that has a waveguide structure in the thickness direction of the cross section perpendicular to the light axis (6), and that generates gain with respect to laser light; a cladding adhered to one surface of the laser medium; and a heat sink (2) adhered to the one surface of the laser medium via the cladding. The laser medium generates a lens effect due to the refractive index distribution, and the laser light oscillates in the waveguide mode in the thickness direction, and oscillates in the spatial mode in the direction perpendicular to the light axis and the thickness direction due to the lens effect. A desired temperature distribution is generated in the laser medium and the refractive index distribution within the laser medium is generated due to the junction area of the cladding and the heat sink (2).

Description

Mode-controlled waveguide laser device

The present invention relates to a mode-controlled waveguide laser device used in a high-power laser device.

Conventionally, in order to realize a laser device capable of high-intensity oscillation, a mode-controlled waveguide laser device shown in FIGS. 9, 10, and 11 has been proposed (see, for example, Patent Document 1).
FIG. 9 is a side view showing a configuration of a conventional mode control waveguide type laser device. 10 is a sectional view of the section aa ′ in FIG. 9 as seen from the laser emission side, and FIG. 11 is a sectional view of the section bb ′ in FIG. 9 as seen from the top.

9 to 11, a conventional mode-controlled waveguide laser device includes an excitation semiconductor laser 101 that emits excitation light, a laser medium 105 that emits laser light, and a cladding that is bonded to the lower surface of the laser medium 105. 104 and a heat sink 102 bonded to the lower surface of the clad 104 by a bonding agent 103.

The laser medium 105 has a flat plate shape, and has a waveguide structure in the thickness direction (y-axis) of the cross section perpendicular to the optical axis 106 (z-axis) representing the laser oscillation direction. It has a periodic lens effect in a direction (x axis) perpendicular to the direction.

An end surface 105a on the incident side of the laser medium 105 is provided with a total reflection film that reflects the laser light, and an antireflection film that reflects part of the laser light and transmits part of the end surface 105b on the emission side. It has been subjected. These total reflection film and partial reflection film are formed by laminating dielectric thin films, for example.

As shown in FIG. 9, when the excitation light emitted from the semiconductor laser 101 enters from the end face 105a of the laser medium 105, the total reflection film on the end face 105a transmits the excitation light and reflects the laser light. It becomes.
As shown in FIGS. 10 and 11, the heat sink 102 has an extended tooth structure parallel to the optical axis 106 (z axis).

The excitation light incident from the end face 105 a of the laser medium 105 is absorbed by the laser medium 105 and generates a gain for the laser light inside the laser medium 105.
Due to the gain generated in the laser medium 105, the laser light oscillates between the end face 105a and the end face 105b perpendicular to the optical axis 106 of the laser medium 105, and a part of the oscillation light passes from the end face 105b to the laser resonator. Output to the outside.

In the conventional mode control waveguide type laser apparatus shown in FIGS. 9 to 11, if the laser output required for the laser apparatus is determined, the necessary pumping power is determined.
Further, the excitation region in the waveguide width direction (x-axis direction) of the excitation light is determined according to the determined power scale of the excitation power, and the mutual interval between the teeth of the extended tooth structure of the heat sink 102 is To depend on.

Japanese Patent No. 4392024

In a conventional mode-controlled waveguide type laser device, the excitation region in the waveguide width direction of the excitation light is determined according to the excitation power corresponding to the laser output required for the laser device, and each tooth of the heat sink depends on the excitation region. Therefore, the control range of the focal length of the generated thermal lens is limited.

The present invention has been made in order to solve the above-described problems, and heat is exhausted over the entire area where heat generation is large, and a thermal lens is generated in the area where heat generation is small, thereby reducing the focal length of the generated thermal lens. It is an object of the present invention to obtain a mode-controlled waveguide type laser device with an extended control range and improved reliability.

A mode-controlled waveguide laser device according to the present invention has a flat plate shape, a waveguide structure in the thickness direction of a cross section perpendicular to the optical axis, and a laser medium that generates a gain for laser light, and a laser A cladding that is bonded to one surface of the medium and a heat sink that is bonded to one surface of the laser medium via the cladding; the laser medium generates a lens effect by a refractive index distribution; Is a mode-controlled waveguide laser device that oscillates in a waveguide mode and oscillates in a spatial mode due to a lens effect in a direction perpendicular to the optical axis and thickness direction. A desired temperature distribution is generated in the medium to generate a refractive index distribution in the laser medium.

According to this invention, it is possible to adjust the refractive index distribution generated in the laser medium and the lens effect by adjusting the bonding area between the clad and the heat sink, and in a place where heat generation is large, the entire surface is exhausted to lower the temperature and generate heat. The reliability can be improved by generating a thermal lens in a small area.

It is a side view which shows the structure of the mode control waveguide type laser apparatus which concerns on Embodiment 1 of this invention. Example 1 FIG. 2 is a cross-sectional view of the a-a ′ cross section in FIG. 1 viewed from the laser emission side. Example 1 FIG. 2 is a cross-sectional view of a b-b ′ cross section in FIG. 1 as viewed from above. Example 1 It is explanatory drawing which shows the example of a calculation result of the temperature distribution in a laser medium at the time of excitation at the time of using the mode control waveguide type laser apparatus of FIG. Example 1 It is explanatory drawing which shows the effect at the time of using the mode control waveguide type laser apparatus of FIG. Example 1 FIG. 5 is a cross-sectional view of a mode-controlled waveguide laser device according to Embodiment 2 of the present invention as viewed from the top along the b-b ′ cross section in FIG. 1. (Example 2) FIG. 5 is a cross-sectional view of a mode-controlled waveguide laser device according to a third embodiment of the present invention viewed from the top along the b-b ′ cross section in FIG. 1. Example 3 FIG. 6 is a cross-sectional view of a mode-controlled waveguide laser device according to a fourth embodiment of the present invention as viewed from the top along the b-b ′ cross section in FIG. 1. (Example 4) It is a side view which shows the structure of the conventional mode control waveguide type laser apparatus. FIG. 10 is a cross-sectional view of the a-a ′ cross section in FIG. 9 viewed from the laser emission side. FIG. 10 is a cross-sectional view of the b-b ′ cross section in FIG. 9 as viewed from above.

Example 1
Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.
1 to 3 are diagrams showing the configuration of a mode-controlled waveguide laser device according to Embodiment 1 of the present invention. FIG. 1 is a side view, and FIG. 2 is a cross-sectional view taken along line aa ′ of FIG. FIG. 3 is a cross-sectional view of the bb ′ cross section of FIG. 1 viewed from above.

1 to 3, a mode-controlled waveguide laser device according to Embodiment 1 of the present invention includes an excitation light incident means 1, a laser medium 5 that emits laser light when the excitation light is incident, and a laser medium. 5 is provided with a clad 4 bonded to the lower surface of 5 and a heat sink 2 bonded to the lower surface of the clad 4 with a bonding agent 3.
The laser medium 5 is formed on a flat plate and has a waveguide structure in the thickness direction of a cross section perpendicular to the optical axis 6 representing the laser oscillation direction or the signal light traveling direction.

In the laser medium 5, the shape of the end faces 5 a and 5 b perpendicular to the optical axis 6 is, for example, rectangular, and typically has a thickness in the y-axis direction of several μm to several tens of μm and a width in the x-axis direction. It has a size of several hundred μm to several mm.

Here, a coordinate system is used in which the long side direction of the

rectangular end faces

5a and 5b is the x axis, the short side direction is the y axis, and the optical axis 6 direction is the z axis.
Note that the

end surfaces

5a and 5b of the laser medium 5 do not necessarily have to be rectangular. For example, the short sides of the

end surfaces

5a and 5b may have an arc shape.

The clad 4 has a refractive index smaller than that of the laser medium 5 and is bonded to one surface parallel to the xz plane of the laser medium 5.
The clad 4 is configured by, for example, depositing a film made of an optical material as a raw material, or optically bonding the optical material to the laser medium 5 by optical contact, diffusion bonding, or the like. Further, as the clad 4, an optical adhesive having a refractive index smaller than that of the laser medium 5 may be used.

The heat sink 2 is made of a material having high thermal conductivity, and has a comb shape (see the hatched portion in FIG. 3) in a part of a cross section (yz plane) parallel to the optical axis 6. The comb-shaped end face of the heat sink 2 is bonded to the clad 4 via the bonding agent 3.
The heat sink 2 has

end surfaces

2a and 2b corresponding to the incident side end surface 5a and the emission side end surface 5b of the laser medium 5, respectively.

The bonding agent 3 can be realized by a metal solder, an optical adhesive, a heat conductive adhesive or the like, and exhausts heat generated in the laser medium 5 to the heat sink 2 via the clad 4.
Note that the lower surface of the clad 4 may be subjected to metallization (attaching a metal film) in order to increase the bonding strength with the bonding agent 3.
Further, when the heat sink 2 is made of an optical material, the clad 4 and the heat sink 2 may be directly bonded by, for example, optical contact or diffusion bonding.

The excitation light incident means 1 is made of, for example, a semiconductor laser and is disposed close to the end face 5 a of the laser medium 5 or, if necessary, coupled optics between the excitation light emission end face and the end face 5 a of the laser medium 5. A system (not shown) is inserted and arranged.
Further, a cooling heat sink (not shown) is joined to the excitation light incident means 1 as necessary.

The excitation light emitted from the excitation light incident means 1 enters the xz plane direction from the end surface 5 a of the laser medium 5 and is absorbed by the laser medium 5.
Here, as an example, the pumping light incident means 1 is a semiconductor laser. However, a semiconductor laser is not necessarily used as long as the laser medium 5 can have a gain.

The end face 5a of the laser medium 5 is provided with a total reflection film that reflects laser light, and the end face 5b is provided with a partial reflection film that transmits part of the laser light. These total reflection film and partial reflection film are formed by laminating dielectric thin films, for example.
When the excitation light emitted from the excitation light incident means 1 is incident from the end face 5a of the laser medium 5, the total reflection film on the end face 5a is an optical film that transmits the excitation light and reflects the laser light. .

As the laser medium 5, a general solid laser material can be used. For example, Nd: YAG, Nd: YLF, Nd: Glass, Nd: YVO4, Nd: GdVO4, Yb: YAG, Yb: YLF, Yb : KGW, Yb: KYW, Er: Glass, Er: YAG, Tm: YAG, Tm: YLF, Ho: YAG, Ho: YLF, Ho: YAG, Ho: YLF, Ti: Sapphire, Cr: LiSAF .

In FIG. 1, the upper surface of the laser medium 5 is in contact with air, but a second cladding (not shown) having a smaller refractive index than the laser medium 5 with respect to the upper surface of the laser medium 5 is used. ) May be joined.

As described above, when the second clad is bonded to the upper surface of the laser medium 5, the propagation mode in the y-axis direction of the laser medium 5 can be arbitrarily set by adjusting the refractive index difference between the laser medium 5 and the second clad. Can be adjusted.
Further, if the thickness of the second cladding in the y-axis direction is set large, the rigidity of the laser medium 5 can be increased without affecting the waveguide mode of the laser medium 5.

Further, a substrate (not shown) may be bonded to the upper surface of the laser medium 5 via a second bonding agent having a smaller refractive index than the laser medium 5.
As the second bonding agent, for example, an optical adhesive is used, and as the substrate, for example, an optical material or metal is used.

As described above, when the second bonding agent and the substrate are bonded to the upper surface of the laser medium 5, by adjusting the refractive index difference between the laser medium 5 and the second bonding agent, the y axis direction of the laser medium 5 is adjusted. The propagation mode can be arbitrarily adjusted.
If the thickness of the substrate in the y-axis direction is set large, the rigidity of the laser medium 5 can be increased without affecting the waveguide mode of the laser medium 5.

Further, when thermal expansion occurs due to the temperature rise of the laser medium 5, the second bonding agent (optical adhesive) has lower rigidity than the crystal or glass material, and deforms according to the expansion of the laser medium 5. The stress applied to the laser medium 5 can be relaxed.

Furthermore, an optical film (not shown) having a refractive index smaller than that of the laser medium 5 is applied to the upper surface of the laser medium 5, and the optical film surface is almost the same as the laser medium 5 by optical contact or diffusion bonding. You may join the board | substrate (not shown) which has a thermal expansion coefficient.

As described above, when the optical film and the substrate are bonded to the upper surface of the laser medium 5, the propagation mode in the y-axis direction of the laser medium 5 is arbitrarily adjusted by adjusting the refractive index difference between the laser medium 5 and the optical film. can do.
If the thickness of the substrate in the y-axis direction is set large, the rigidity of the laser medium 5 can be increased without affecting the waveguide mode of the laser medium 5.

Further, since the laser medium 5 and the substrate have substantially the same thermal expansion coefficient, when thermal expansion occurs due to the temperature increase of the laser medium 5, the substrate also expands at substantially the same rate.
At this time, the optical film between the laser medium 5 and the substrate has a lower density and lower rigidity than a crystal or glass material. Therefore, the optical film is deformed in accordance with the expansion of the substrate and relaxes the stress applied to the laser medium 5. It is possible.
Further, when the optical film and the substrate are bonded, it is possible to increase the bonding strength by selecting an optical film material and a substrate that are easy to optically bond.

Next, referring to FIG. 2 and FIG. 3, in the mode control waveguide type laser apparatus of FIG. 1, a desired temperature distribution is generated in the laser medium 5 to generate a refractive index distribution in the laser medium 5. A method for generating a lens effect from this refractive index distribution will be described.

In FIG. 3, focusing on the heat sink 2, in order to clarify the difference between the bonding region bonded to the cladding 4 via the bonding agent 3 and the region not bonded to the cladding 4, the cladding 4 is bonded via the bonding agent 3. The joining region (comb shape) of the heat sink 2 to be joined with is shown by hatching.
Also, as shown in FIG. 3, the total length of the laser medium 5 in the direction of the optical axis 6 (z-axis) is Lo, and the width of the comb structure portion installed in a part of the optical axis direction is A.
In this case, the joint part (adjustment side for forming the width A) of the comb structure is provided on the end face 2 b, that is, the emission side of the optical axis 6.

When the excitation light incident from the end face 5a of the laser medium 5 is absorbed by the laser medium 5, a part of the power of the absorbed excitation light is converted into heat to generate heat, and the generated heat is generated in the cladding 4 and the junction. Heat is discharged to the heat sink 2 through the agent 3.

At this time, when the heat sink 2 is comb-shaped in the direction of the optical axis 6 and the range bonded by the bonding agent 3 is only the tip portion of the comb teeth, two combs are provided at the center portion between the two comb teeth. A heat flow is generated on both sides in the x-axis direction from the substantially central portion of the tooth. Therefore, the temperature at the substantially central portion of the two comb teeth becomes the maximum, and the temperature decreases as the portion approaches the comb teeth portion.

On the other hand, the optical material such as the laser medium 5 changes in refractive index almost in proportion to the temperature difference, and a material having a positive refractive index change dn / dT per unit temperature is used as the optical material of the laser medium 5. The refractive index at the center of the two comb teeth having a high temperature increases, and the refractive index decreases as it approaches the comb tooth portion.
As a result, a thermal lens effect is generated in the x-axis direction with the center portion of the two comb teeth as the optical axis.

Similarly, when a material having a negative refractive index change dn / dT per unit temperature is used as the optical material of the laser medium 5, the refractive index distribution is opposite to the temperature distribution, and the portion of the portion bonded to the comb teeth is used. The refractive index is large, and the refractive index at the center of the two comb teeth is small.
As a result, in the x-axis direction, a thermal lens effect is generated with the portion bonded to the comb teeth as the optical axis. Since the same effect can be obtained regardless of whether dn / dT is positive or negative, the following description will be made using the case where dn / dT is positive unless otherwise specified.

Here, the width A of the comb structure portion in the direction of the optical axis 6 (z-axis) is changed from A / Lo = 0 (when no comb structure exists in the optical axis direction of the heat sink 2) to A / Lo = 1. In this case, the temperature distribution generated in the laser medium 5 can be changed by changing to the case (when the heat sink 2 has a comb structure in the entire optical axis direction).
Therefore, the thermal lens effect generated in the laser medium 5 can be adjusted.

Next, referring to FIGS. 4 and 5, in the first embodiment of the present invention shown in FIGS. 1 to 3, when the width A of the comb structure portion in the optical axis direction is set to A / Lo = 0 ( A description will be given of a case in which the change is made from the case where the comb structure does not exist in the optical axis direction of the heat sink 2 to the case where A / Lo = 1 (when the comb structure is provided in the entire optical axis direction of the heat sink 2).

4 and 5 are explanatory diagrams showing calculation examples and effects when Nd: YVO4 is used as the laser medium 5. As a calculation condition, the width of the laser medium 5 (x-axis direction) = 200 μm at room temperature of 25 ° C. , Laser thickness (y-axis direction) = 40 μm, excitation width (same as comb tooth interval in the direction parallel to the optical axis 6) = 200 μm, excitation light power = 10 W (emission wavelength: 808 nm), laser light wavelength = 1.064 μm Shows the case.

FIG. 4 shows the temperature distribution in the x-axis direction (0 to 200 μm) at the center of the y-axis direction of the laser medium 5 at the time of excitation, the broken line is the temperature distribution when A / Lo = 0, and the solid line is A / Lo = 1. In the case of temperature distribution.
FIG. 5 shows a change in Diopter [1 / m] (the reciprocal of the thermal lens focal length). When the width A of the comb structure portion is changed from A / Lo = 0 to A / Lo = 1, FIG. The change of Diopter is shown.

4 and 5, when the entire laser medium 5 is uniformly excited and A / Lo = 0, the thermal lens focal length generated in the laser medium 5 is 2.9 m (Diopter = 0.4 [ 1 / m]).
When A / Lo = 1, the thermal lens focal length generated in the laser medium 5 is 74.3 mm (Diopter = 13.46 [1 / m]).
That is, by changing the width A from “0” to “1”, the focal length of the thermal lens can be arbitrarily adjusted in the range of “2.9 m to 74.3 mm”.

Similarly, even when a part of the laser medium 5 is locally excited, there is no comb structure in the direction of the optical axis 6 (z axis) and there is a comb structure in the entire optical axis direction. Since the efficiency of exhaust heat differs, it is clear that the focal length of the thermal lens can be adjusted by changing the width A of the comb structure portion.

Further, for example, in the case of end surface excitation in which excitation is performed from the end surface 5a side in the optical axis direction of the laser medium 5, the comb structure can be installed on the end surface 5a side on the incident side.
As described above, in the case of end-face excitation in which excitation is performed from the end face 5a side of the laser medium 5, the temperature rise in the laser medium 5 is highest on the end face 5a side, and the temperature distribution on the end face 5a side is most prominent. The thermal lens focal length can be most easily adjusted by installing a joint having a comb structure on the side end face 5a side.

Further, in the case of end face excitation in which excitation is performed from the end face 5a side on the incident side, the comb structure may be installed on the end face 5b side on the output side, and when the joint portion having the comb structure is arranged on the end face 5b side, Since the joining surface area with the heat sink 2 is increased on the incident side end face 5a side, the efficiency of exhaust heat is improved.
As a result, the thermal lens effect generated in the laser medium 5 can be adjusted, and the thermal lens effect can be suppressed.

Although the case of end face excitation in which excitation is performed from the end face 5a side has been described as an example, the optical system in the direction of the optical axis 6 (z axis) is asymmetrical at both end faces 5a, 5b of the laser medium 5, and the laser medium 5 It is obvious that the same effect can be obtained by installing the comb structure portion when the temperature distribution in the inside is distributed in the optical axis direction.
Further, the comb structure in the optical axis direction in the laser medium 5 may be provided on both end faces 5a and 5b of the laser medium.
With this configuration, the thermal lens focal length can be adjusted even when a temperature distribution symmetrical in the laser optical axis direction in the laser medium 5 occurs, such as side excitation.

In addition, although the space | gap between the comb teeth of the heat sink 2 is normally air, you may fill with the heat insulating material which has a thermal conductivity smaller than the heat sink 2. FIG. In this case, the refractive index distribution in the laser medium 5 is generated by the temperature distribution generated by the difference in thermal conductivity between the tip of the comb teeth and the thermal insulating material.
By burying the heat insulating material in this way, the front surface on the exhaust heat side of the clad 4 is bonded to the bonding agent 3 and the heat generated in the laser medium 5 is exhausted, so that the temperature rise of the laser medium 5 is suppressed. be able to. Further, the rigidity of the heat sink 2 can be increased as compared with the case where the clad 4 is fixed only by the comb-shaped tip.

As described above, the mode-controlled waveguide laser device according to the first embodiment (FIGS. 1 to 5) of the present invention has a flat plate shape and is guided in the thickness direction of the cross section perpendicular to the optical axis 6. A laser medium 5 having a waveguide structure and generating a gain for laser light; a clad 4 joined to one surface of the laser medium 5; a heat sink 2 joined to one surface side of the laser medium 5 via the clad 4; The laser medium 5 generates a lens effect based on the refractive index distribution, and the laser light oscillates in a waveguide mode in the thickness direction, and also due to the lens effect in a direction perpendicular to the optical axis 6 and the thickness direction. Oscillates in spatial mode.

In the above configuration, a desired temperature distribution is generated in the laser medium 5 according to the bonding area between the clad 4 and the heat sink 2 to generate a refractive index distribution in the laser medium 5.
Specifically, the heat sink 2 includes a joint portion (hatched portion in FIG. 3) having a comb structure parallel to the optical axis 6 in a part of the optical axis 6 of the laser light, and adjusts the range of the comb structure. Thus, a desired temperature distribution is generated in the laser medium to generate a refractive index distribution in the laser medium.

As described above, the junction area between the clad 4 and the heat sink 2 can be adjusted to adjust the refractive index distribution and the lens effect generated in the laser medium 5. By generating a thermal lens at a location where heat generation is small, a mode-controlled waveguide laser device with improved reliability can be realized.

Further, in FIG. 3, the joint portion (open portion on the adjustment side) having a comb structure is installed on the joint surface excluding the incident surface on which the laser beam of the optical axis 6 of the laser medium 5 is incident.
That is, the joint portion having the comb structure is disposed on the end surface 2b side, that is, the joint surface of the emission surface (end surface 5b) from which the laser beam of the optical axis 6 of the laser medium 5 is emitted, and does not constitute a comb tooth. Is disposed on the end surface 2a side, that is, on the joint surface of the incident surface (end surface 5a) of the laser medium 5.

This makes it possible to suppress heat generation on the incident side where the temperature is likely to rise.

(Example 2)
In the first embodiment (FIGS. 1 to 5), in order to adjust the thermal lens generated in the laser medium 5, a comb structure is formed on a part of the heat sink 2 in the direction of the optical axis 6 (z axis). The temperature distribution in the waveguide is adjusted by adjusting the width A of the comb structure portion. However, as shown in FIG. 6, even if a plurality of comb structure portions in the optical axis direction of the heat sink 2 are provided intermittently, Good.

The second embodiment of the present invention will be described below with reference to FIGS.
FIG. 6 is a cross-sectional view showing the shape of the heat sink 2 of the mode control waveguide type laser apparatus according to Embodiment 2 of the present invention, and shows the cross section bb ′ of FIG.
In this case, the entire configuration is as shown in FIG. 1 except that the comb shape of the heat sink 2 is different from that described above. Unless otherwise specified, the excitation light incident means 1 to the laser medium 5 described above (FIG. 1). It shall have the same function.

In the case where a single comb structure is provided as in the first embodiment (FIGS. 1 to 3), as the width A (see FIG. 3) of the comb structure portion in the optical axis direction of the heat sink 2 becomes narrower, the clad 4 and the heat sink 2 are increased in area, and a heat distribution generated by exhaust heat causes a refractive index distribution in the y-axis direction, resulting in a thermal lens in the y-axis direction.
On the other hand, according to the second embodiment (FIG. 6) of the present invention, the above problem (generation of a thermal lens in the y-axis direction) is caused by intermittently providing a plurality of comb structure portions in the optical axis direction of the heat sink 2. ) Can be eliminated.

In FIG. 6, a plurality of comb structures in the optical axis direction of the heat sink 2 are intermittently arranged, and the focal length of the thermal lens generated in the laser medium 5 can be adjusted by adjusting the width of each comb structure portion. It is.
Also, the focal length of the thermal lens can be adjusted by adjusting the number of comb structures having a certain width.
In FIG. 6, the width of each comb structure portion is constant, but each width is not necessarily uniform.

As described above, according to the mode-controlled waveguide laser device according to the second embodiment (FIGS. 1 and 6) of the present invention, the joint portion having the comb structure is the laser beam on the optical axis 6 of the laser medium 5. Are intermittently provided from the incident surface on which the light is incident, a portion where the heat sink 2 and the clad 4 are joined via the bonding agent 3 in the direction of the optical axis 6 (z axis), and the heat sink 2 and the clad 4. And the portions where the and are not joined are alternately distributed.
This increases the heat conduction in the optical axis direction. As a result, the heat distribution generated in the y-axis direction can be averaged in the direction parallel to the optical axis 6 and the generation of thermal lenses in the y-axis direction is reduced. can do.

As described above, the gap between the comb teeth of the heat sink 2 is usually air, but may be filled with a heat insulating material having a lower thermal conductivity than the heat sink 2. In this case, the refractive index distribution in the laser medium 5 is generated by a temperature distribution generated by a difference in thermal conductivity between the tip of the comb teeth and the thermal insulating material.
By burying the heat insulating material in this way, the front surface on the exhaust heat side of the clad 4 is bonded to the bonding agent 3 and the heat generated in the laser medium 5 is exhausted, so that the temperature rise of the laser medium 5 is suppressed. be able to. Further, the rigidity of the heat sink 2 can be increased as compared with the case where the clad 4 is fixed only by the comb-shaped tip.

(Example 3)
Although not particularly mentioned in the first and second embodiments (FIGS. 1 to 6), in laser oscillation in the x-axis direction in the laser resonator, the width (x-axis) of the laser medium 5 is Since it is sufficiently larger than the wavelength of the laser beam, mode selection by the waveguide in the y-axis is not performed, and a spatial mode laser resonator is obtained.
Therefore, as shown in FIG. 7, a plurality of comb teeth bonded to the clad 4 via the bonding agent 3 are provided in a direction parallel to the optical axis 6 of the heat sink 2, and two in the x-axis direction in the laser medium 5 are provided. A plurality of oscillation modes that are periodic in the x-axis direction may be generated by periodically generating a thermal lens effect having the center of the comb teeth as the optical axis.

The third embodiment of the present invention will be described below with reference to FIGS.
FIG. 7 is a cross-sectional view showing the shape of the heat sink 2 of the mode control waveguide type laser apparatus according to Embodiment 3 of the present invention, and shows the cross section bb ′ of FIG.
In this case, the entire configuration is as shown in FIG. 1 except that the comb shape of the heat sink 2 is different from that described above. Unless otherwise specified, the excitation light incident means 1 to the laser medium 5 described above (FIG. 1). It shall have the same function.

In Embodiment 3 of the present invention, a desired temperature distribution is generated in the laser medium 5 to generate a refractive index distribution in the laser medium 5, and a plurality of lenses are arranged in the x-axis direction based on this refractive index distribution. A lens effect that is an effect is generated, and a mode-controlled waveguide laser device that oscillates in a waveguide mode in the y-axis direction and oscillates in a spatial mode by the lens effect in the x-axis direction is realized.

In FIG. 7, the width A (see FIG. 3) of the comb structure in the direction of the optical axis 6 (z-axis) of the heat sink 2 is determined when the comb structure does not exist in the optical axis direction (when the portions of the comb structures are in contact with each other). The focal length of the thermal medium of the laser medium 5 is adjusted by changing until the entire optical axis direction has a comb structure, or by adjusting the number of comb structure portions existing in the optical axis direction. be able to.

As described above, according to the mode-controlled waveguide laser device according to the third embodiment (FIGS. 1 and 7) of the present invention, the user medium 2 has the optical axis 6 and the thickness direction due to the refractive index distribution. A lens effect that is an effect of arranging a plurality of lenses in a direction perpendicular to (x-axis) is generated, and the laser light oscillates in a waveguide mode in the thickness direction (y-axis), and the optical axis 6 and thickness In the direction perpendicular to the direction (x-axis), a plurality of oscillations occur in the spatial mode due to the lens effect.

According to the configuration of FIG. 7, high output power can be achieved by using a broad area LD having a wide light emitting region that is easy to achieve high output, and an LD array in which emitters are arranged in a row, thereby increasing the output power of excitation light. Even in the mode control waveguide type laser apparatus capable of outputting the laser beam, the thermal lens generated in the laser medium 5 can be controlled.

Example 4
In the third embodiment (FIG. 7), in order to adjust the thermal lens focal length generated in the laser medium 5, a plurality of lens effects are generated in the x-axis direction, and in the waveguide mode in the y-axis direction. In a device that oscillates and oscillates in a spatial mode due to the lens effect in the x-axis direction, a comb structure is provided in the optical axis direction of the heat sink 2, and the width A of the comb structure part or the number of comb structure parts existing is adjusted. Thus, the temperature distribution in the waveguide is adjusted. However, as shown in FIG. 8, a plurality of comb structures in the direction of the optical axis (z-axis) of the heat sink 2 may be provided intermittently.

The fourth embodiment of the present invention will be described below with reference to FIGS.
FIG. 8 is a cross-sectional view showing the shape of the heat sink 2 of the mode control waveguide type laser apparatus according to Embodiment 4 of the present invention, and shows the cross section bb ′ of FIG.
In this case, the entire configuration is as shown in FIG. 1 except that the comb shape of the heat sink 2 is different from that described above. Unless otherwise specified, the excitation light incident means 1 to the laser medium 5 described above (FIG. 1). It shall have the same function.

In the case of the above-described third embodiment (FIG. 7), as the comb structure portion of the heat sink 2 in the optical axis direction becomes narrower, a refractive index distribution is also generated in the y-axis direction due to heat distribution generated by exhaust heat. As a result, a thermal lens is also generated in the y-axis direction.
On the other hand, according to Embodiment 4 (FIG. 8) of the present invention, a desired temperature distribution is generated in the laser medium 5 by intermittently providing a plurality of comb structure portions in the optical axis direction of the heat sink 2. Then, a refractive index distribution is generated in the laser medium 5, and a lens effect that is an effect of arranging a plurality of lenses in the x-axis direction is generated by the refractive index distribution, and oscillation is performed in a waveguide mode in the y-axis direction. In the x-axis direction, the above problem can be solved even in an apparatus that oscillates in a spatial mode due to the lens effect.

In FIG. 8, a plurality of comb structure portions in the direction of the optical axis (z axis) of the heat sink 2 are intermittently arranged, and the width A (see FIG. 3) of the comb structure portion is adjusted to adjust the inside of the laser medium 5. It is possible to adjust the focal length of the thermal lens generated in the above, and it is also possible to adjust the focal length of the thermal lens generated in the laser medium 5 by adjusting the number of comb structures having a certain width.
In addition, the width A of each comb structure part does not necessarily need to be constant.

As described above, according to the mode-controlled waveguide laser device according to the fourth embodiment (FIGS. 1 and 8) of the present invention, the heat sink 2 and the clad 4 are bonded via the bonding agent 3 in the optical axis direction. By alternately distributing the portions to be joined and the portions not to be joined, heat conduction in the direction parallel to the optical axis 6 is increased. As a result, even in a laser apparatus having a plurality of oscillation modes that are periodic in the x-axis direction, y The heat distribution generated in the axial direction can be averaged in the direction parallel to the optical axis 6, and the thermal lens in the y-axis direction can be reduced.

In addition, it is possible to increase the output of pumping light and output high-power laser light by using a broad area LD with a wide light-emitting area that can easily achieve high output and an LD array in which emitters are arranged in a row. Even in such a mode-controlled waveguide laser device, the thermal lens generated in the laser medium 5 can be controlled.

In the first to fourth embodiments, the entire surface is exhausted on the incident side where heat generation is large, and the thermal lens is adjusted and generated on the emission side where heat generation is small. Therefore, as shown in FIGS. The joint portion having the structure is disposed on the joint surface of the emission surface (end surface 5b) from which the laser beam of the optical axis 6 of the laser medium 5 is emitted. If priority is given to the above, a joint portion having a comb structure may be provided on the joint surface of the incident-side end surface 5a having a strong temperature distribution.

1 Excitation light incident means 2 Heat sink 3 Adhesive 4 Cladding 5 Laser medium 5a 5b End face 6 Optical axis.

Claims

A laser medium having a flat plate shape, having a waveguide structure in a thickness direction of a cross section perpendicular to the optical axis, and generating a gain for laser light;
A clad bonded to one surface of the laser medium;
A heat sink joined to the one surface side of the laser medium via the clad,
The laser medium generates a lens effect by a refractive index distribution,
The laser light is a mode-controlled waveguide laser device that oscillates in a waveguide mode in the thickness direction and oscillates in a spatial mode due to the lens effect in a direction perpendicular to the optical axis and the thickness direction. And
A mode-controlled waveguide laser device that generates a desired temperature distribution in the laser medium based on a junction area between the clad and the heat sink to generate the refractive index distribution in the laser medium.
The laser medium generates a lens effect that is an effect of arranging a plurality of lenses in a direction perpendicular to the optical axis and the thickness direction, based on the refractive index distribution,
2. The laser light oscillates in a waveguide mode in the thickness direction and a plurality of oscillations in a spatial mode due to the lens effect in a direction perpendicular to the optical axis and the thickness direction. A mode-controlled waveguide laser device described in 1.
The heat sink includes a joint having a comb structure parallel to the optical axis in a part of the optical axis of the laser light,
The mode according to claim 1 or 2, wherein a desired temperature distribution is generated in the laser medium by adjusting a range of the comb structure to generate a refractive index distribution in the laser medium. Control waveguide type laser device.
The mode-controlled waveguide laser device according to claim 3, wherein the joint portion having the comb structure is disposed on a joint surface of an incident surface on which laser light having an optical axis of the laser medium is incident.
5. The mode control waveguide type according to claim 3, wherein the joint portion having the comb structure is disposed on a joint surface of an emission surface from which a laser beam having an optical axis of the laser medium is emitted. Laser device.
4. The mode-controlled waveguide laser device according to claim 3, wherein the joint portion having the comb structure is disposed on a joint surface excluding an incident surface on which laser light having an optical axis of the laser medium is incident.
The mode control waveguide according to claim 3, wherein the joint portion having the comb structure is disposed on a joint surface excluding an emission surface from which a laser beam having an optical axis of the laser medium is emitted. Type laser equipment.
The junction part having the comb structure is provided with a plurality of intermittently from an incident surface on which a laser beam having an optical axis of the laser medium is incident. 8. A mode-controlled waveguide laser device described in 1.